If you follow the controller wiring diagram it should work.
But if you wired it wrong, chances are the mosfet was damaged and permanently shorted.
So ensure it's still ok. Remove the power, disconnect the handle and check the resistance between 24V and T12+.
If it reads low resistance, it's gone!
It's strange they use Earth wire for the switch and NTC, but it's probably the same as T12-, check if they're connected together in the board.
Likely they use a different ground path to minimize the error caused by the voltage drop when the heater is running.
If not connected together, then connect the sensor and switch to T12- instead and try again.